1. Field of the Invention
The present invention relates to an electron beam exposure apparatus and an electron beam exposure method for drawing a circuit pattern by use of electron beam.
2. Related Art
According to electron beam lithography, particularly according to an electron beam direct writing technology, when a device circuit pattern is exposed into a resist on a semiconductor substrate, masks used as a master of circuit pattern need not to be fabricated for each device. Therefore, there is an advantage in that it is possible to reduce fabrication cost and period.
Additionally, the wavelength of electron beam is significantly shorter than that of the light source of photoexposure, thus enabling shaping of a fine pattern. Therefore, the above technique has been used for device prototyping by QTAT (Quick Turn Around Time), R&D of the most advanced fine devices and the like.
In electron beam lithography using the electron beam direct writing technology, a circuit pattern to be exposed is divided into basic figures acting as an exposure unit, and then beams having the same shape and size as each basic figure are shaped by use of a plurality of shaping patterns. Electron beams shaped with the shaping aperture are directly irradiated on the resist to perform an exposure processing. Individual electron beam irradiations are called a shot.
As the electron beam shaping technique by the electron beam direct drawing technique, there have been known two methods: Variable Shaped Beam (VSB) technique and Character Projection (CP) technique.
According to VSB technique, a rectangular beam shaped by a first shaping aperture is irradiated on part of an opening having the same rectangular shape of a second shaping aperture to shape a rectangular (oblong) beam of a given size.
According to CP technique, a rectangular beam shaped by a first shaping aperture is irradiated on an opening of a given shape formed in a second shaping aperture to shape a beam having the same shape as the opening. The resultant beam shape is called a character, and the opening is called a character opening.
In the electron beam writing based on CP technique, exposure can be performed with a beam shape corresponding to a character opening preliminarily formed in the second shaping aperture. Thus, compared to in the case that beam irradiation using basic shapes is repeated, as with VSB method, to shape a pattern of a given shape, the number of shots can be reduced and drawing time can also be shortened.
The present inventor has proposed a technique of arranging as a character in a second shaping aperture a standard cell constituting a logic device in order to efficiently draw the logic device pattern of small production type directly on a wafer using the electron beam writing based on CP technique (refer to Japanese Patent Laid-Open No. 2001-274071).
However, as semiconductor device patterns are miniaturized, the size of cell in the device also becomes smaller. Accordingly, even if individual standard cells are provided as a character, the number of shots per wafer increases, thereby making it impossible to shorten drawing time and thus lowering drawing throughput.